1. Field of the Invention
The present invention relates to a method for estimating a force exerted on a tire or estimating change of a condition of contact with a ground of a tire (hereinafter, referred to contact condition of a tire) exhibited at the time when a running state of a vehicle is changed and an apparatus for putting the method into operation and also relates to the tire with sensors disposed therein.
2. Description of the Related Art
In order to improve a running stability of a vehicle, it is required to feedback forces generated on the tire (generating motive force in tire) such as a load, lateral force or longitudinal force upon estimating them accurately. Relying on the information concerned with those load and forces, it has been considered that improvement in the stability would be further enhanced in view of feasibility of realization of apparatus for controlling the vehicle attitude in a high technical level such as ABS brake and application thereof.
Hitherto, as a method for estimating the force produced in the tire, the tire sensor has been considered and a couple of methods have been proposed. One of them is exemplified by FIG. 8, (a) and (b) such that the deformation amount produced in the inner liner portion 52 is measured by sensor 53 such as strain gauge for measuring the deformation amount disposed at at least two positions, and from those measured deformation amount, the dynamic condition of the tire, which is exhibited at the time when a load, lateral force or longitudinal force is exerted on the tire, is estimated. Also, a method for obtaining a force of contact with a ground of the tire (hereinafter referred as a contact force of a tire) has been proposed. Namely, the sensor is provided with a pressure sensitive electrical conductive rubber and a DC power source connected in series therewith and the contact force of the tire can be obtained from the change of the resistance value of the conductive rubber caused by the force exerted vertically on the block portion exhibited at the time when the tire contacts with the ground (for example, see patent documents 1 and 2).
On the other hand, a magnetic tire can be used and this tire is provided with many bands of magnetic poles with those poles alternatively changeably positioned formed by magnetizing the magnetizable minute particles mixed into the rubber of tire. The magnetic signature of tire is obtained through the SWT system (torsion measuring system provided in the wall side). The SWT system is located on the portion facing the tire side portion of the suspension strut and is employed for detecting the magnetic field produced by the magnetic tire so as to obtain the magnetic signature. The condition under subjected to damage can be judged by comparing with the foregoing magnetic signature with undamaged one as disclosed by, for example, the patent documents as undergiven.    1 [Patent Document 1] Japanese Laid Open Patent Application No. 2005-343281    2 [Patent Document 2] Japanese Laid Open Patent Application No. 2005-82010    3 [Patent Document 3] Japanese Laid Open Patent Application No. 2005-522680